The personal watercraft includes a cooling system configured to cool an engine and engine oil. As an example of the cooling system, Japanese Laid-Open Patent Application Publication No. 2007-315336 discloses an open-loop water cooling system. In this open-loop water cooling system, water in a sea, a lake or a river, which is around the watercraft, is suctioned by a pump for use as a coolant for cooling the engine and the engine oil. As the pump in this system, a water jet pump is typically used.
Typically, the water ejected from the pump is sent to an exhaust system through an oil cooler, using one of a plurality of systems. In the oil cooler, the water exchanges heat with the engine oil so that the engine oil is controlled to have a suitable temperature. The water in the exhaust system is guided to a passage formed within an engine body. Inside the engine body, the water exchanges heat with a wall surface of the engine so that the engine is controlled to have a suitable temperature. Then, the water is drained from the inside of the engine body outside the watercraft.
The temperature of water suctioned as the coolant varies depending on season, environment, etc. In the winter season, the temperature of the water tends to be lower than in the summer season. In the winter season, after the engine starts, such cold water is sent to the inside of the engine body. For this reason, a relatively long time is required to warm up and efficiently run the engine. In this case, since the temperature of the engine is difficult to increase, the temperature of the engine oil is difficult to increase.
The water ejected from the pump is sent to the oil cooler before being sent to the exhaust system, the interior of the engine body, etc. Such routing makes it difficult to increase the temperature of the engine in the winter season.
In general, engine components are suitably lubricated or sealed by the engine oil having a suitable temperature. In the winter season, however, a relatively long time is required to increase the temperature of the engine oil up to a suitable one.